The application claims priority to Japanese patent application number 2001-095505 filed Mar. 29,2001.
1. Field of the Invention
This invention relates to a zoom actuating apparatus for a camera, wherein an opening or closing operation of a lens barrier and, when necessary, a projecting or retracting operation of an electronic flashlight are performed within a period of shifting of a movable cylinder of a lens barrel from a collapsed state to a wide end or from the wide end to the collapsed state.
2. Description of the Related Art
Cameras, in which a movable cylinder of a lens barrel is delivered forwardly along an optical axis direction from a camera main body and a photograph is thereby taken, have heretofore been constituted such that, for example, in accordance with an operation for preparing for photographing, in which an electric power source button is set in an on state, the movable cylinder is shifted from a collapsed state, in which the movable cylinder is accommodated within the camera main body, to a wide end for wide angle photographing. Also, in accordance with a zooming operation, the movable cylinder is shifted to a tele end for telephotographing. Further, within the period of shifting of the movable cylinder from the collapsed state to the wide end or from the wide end to the collapsed state, an opening or closing operation of a lens barrier, which covers a lens opening section formed in a front cover for forward and backward movements of the movable cylinder of the lens barrel, is performed. In the cases of cameras, in which an electronic flashlight is housed in a camera main body, a projecting or retracting operation of the electronic flashlight is finished within the period of shifting of the movable cylinder from the collapsed state to the wide end or from the wide end to the collapsed state. A camera constituted in such a manner is described in, for example, Japanese Unexamined Patent Publication No. 2000-111975.
Movements of the movable cylinder along the optical axis direction are performed with a helicoid mechanism, which is formed between the movable cylinder and a fixed cylinder for holding the movable cylinder. By way of example, the movable cylinder is actuated for rotation by zoom actuating means. In several types of cameras, the opening or closing operation of the lens barrier and the projecting or retracting operation of the electronic flashlight are performed in the manner interlocked with the actuation by the zoom actuating means for moving the movable cylinder along the optical axis direction.
FIG. 6A is a timing chart showing a first example of an operation of a movable cylinder of a lens barrel and operations interlocked with the operation of the movable cylinder in a conventional camera. FIG. 6B is a timing chart showing a second example of an operation of a movable cylinder of a lens barrel and operations interlocked with the operation of the movable cylinder in a conventional camera. FIGS. 6A and 6B show the cases where the movable cylinder of the lens barrel is operated from the collapsed state to the tele end. In the first example shown in FIG. 6A, the helicoid mechanism is always in an engaged state, and the movable cylinder is delivered linearly from the collapsed state via the wide end to the tele end. Also, within the period of movement of the movable cylinder from the collapsed state to the wide end along the optical axis direction, the lens barrier is operated from a closed state to an open state, and the electronic flashlight is operated from a housed state (i.e., a down state) to a projected state (i.e., an up state). In the second example shown in FIG. 6B, the helicoid mechanism is always in an engaged state. However, in the second example, the zoom actuating means is provided with a gear idling region indicated by the broken line in FIG. 6B, which gear idling region is formed as part of the region ranging from the collapsed state to the wide end. In the gear idling region, the movable cylinder is not rotated and not moved along the optical axis direction. Also, in the second example, by the zoom actuating means which is operating in the gear idling region, the lens barrier is operated from the closed state to the open state, and the electronic flashlight is operated from the housed state to the projected state.
However, in the first example shown in FIG. 6A, the operation of the zoom actuating means is always accompanied by the movement of the movable cylinder along the optical axis direction. Therefore, in cases where the collapsed state of the movable cylinder and the wide end of the movable cylinder are close to each other, and the distance of movement of the movable cylinder between the collapsed state and the wide end along the optical axis direction is short, it becomes necessary to utilize interlocking mechanisms, with which the opening or closing operation of the lens barrier and the projecting or retracting operation of the electronic flashlight are capable of being performed quickly within a short period of the movement of the movable cylinder between the collapsed state and the wide end along the optical axis direction. However, it is not always easy to constitute such interlocking mechanisms. Particularly, as the camera size is made small in recent years, the distance between the lens barrier, which is associated with the camera main body, and the front end of the movable cylinder along the optical axis direction becomes short. In such cases, it is necessary for the opening operation of the lens barrier to be performed quickly within a short period before the front end of the movable cylinder strikes against the lens barrier. In such cases, the reliability, with which the opening operation of the lens barrier is performed quickly, cannot always be kept high.
In the second example shown in FIG. 6B, in cases where the distance of movement of the movable cylinder between the collapsed state and the wide end along the optical axis direction is short, the opening or closing operation of the lens barrier and the projecting or retracting operation of the electronic flashlight are capable of being performed. However, in the second example, wherein the zoom actuating means is provided with the gear idling mechanism, the gear system cannot be kept simple. Therefore, the second example described above is not advantageous from the view point of reduction in camera size and reduction in cost of the camera.
The primary object of the present invention is to provide a zoom actuating apparatus for a camera, wherein an opening or closing operation of a lens barrier is performed with a simple mechanism when a movable cylinder of a lens barrel shifts from a collapsed state to a wide end or from the wide end to the collapsed state.
Another object of the present invention is to provide a zoom actuating apparatus for a camera, wherein the opening or closing operation of the lens barrier and a projecting or retracting operation of an electronic flashlight are performed with a simple mechanism when the movable cylinder of the lens barrel shifts from the collapsed state to the wide end or from the wide end to the collapsed state.
The present invention provides a zoom actuating apparatus for a camera, the apparatus comprising:
i) a lens barrel provided with a fixed cylinder, a movable cylinder supported in the fixed cylinder such that the movable cylinder is capable of moving along an optical axis direction, and a helicoid mechanism for moving the movable cylinder along the optical axis direction through engagement of an internal helicoid, which is formed on an inner circumferential surface of the fixed cylinder, and an external helicoid, which is formed on an outer circumferential surface of the movable cylinder,
ii) zoom actuating means for actuating the movable cylinder for rotation, and
iii) a lens barrier interlocked with the rotation of the movable cylinder such that the lens barrier operates to open or close an opening section formed in a front cover, through which opening section the movable cylinder moves forwardly and backwardly, in accordance with the rotation of the movable cylinder,
wherein the helicoid mechanism is provided with an unengaged region, in which the internal helicoid and the external helicoid are in an unengaged state, within a rotation region between a collapsed state of the movable cylinder and a wide end of the movable cylinder, and
the opening or closing operation of the lens barrier is performed by the rotation of the movable cylinder in the unengaged region of the helicoid mechanism.
The zoom actuating apparatus for a camera in accordance with the present invention may be modified such that a projecting or retracting operation of an electronic flashlight is also performed by the rotation of the movable cylinder in the unengaged region of the helicoid mechanism.
Also, the zoom actuating apparatus for a camera in accordance with the present invention should preferably be modified such that the helicoid mechanism comprises:
a) a flat section, which is formed at a certain part of the internal helicoid of the fixed cylinder, the flat section extending in a direction normal to the optical axis direction and at a position of an end of the internal helicoid,
b) a cam groove, which continues from the flat section and extends in parallel with the internal helicoid, a groove wall of the cam groove, which groove wall is formed on the side opposite to the flat section, is projected beyond the position of the flat section, and
c) a protrusion, which is formed at a certain part of the external helicoid of the movable cylinder and is capable of coming into engagement with the cam groove from a state in abutment with the flat section, and
the state, in which the protrusion is in abutment with the flat section, is set as the unengaged region of the helicoid mechanism.
With the zoom actuating apparatus for a camera in accordance with the present invention, the helicoid mechanism formed between the movable cylinder and the fixed cylinder is provided with the unengaged region, in which the internal helicoid and the external helicoid are in the unengaged state, within the rotation region between the collapsed state of the movable cylinder and the wide end of the movable cylinder. Also, the opening or closing operation of the lens barrier is performed by the rotation of the movable cylinder in the unengaged region of the helicoid mechanism. Therefore, it is not necessary for an idling mechanism to be located in a gear system of zoom actuating means, and the opening or closing operation of the lens barrier is capable of being performed in the state, in which the movable cylinder does not move along the optical axis direction. Accordingly, in cases where the spacing between the front end of the movable cylinder and the lens barrier is small, the opening or closing operation of the lens barrier is capable of being performed reliably. Also, the helicoid mechanism is simple and reliable. The zoom actuating apparatus for a camera in accordance with the present invention is advantageous from the view point of reduction in camera size and reduction in cost of the camera.